Carbon (C) may be considered as the most miraculous element of nature, it becomes an integral element for constituting life on earth, and all organisms are rich in carbon. Carbon may also constitute a large amount of materials with peculiar properties, for example, it may not only constitute the known, hardest diamond, but also softer graphite. In the nano world, in addition to the formation of miraculous carbon nanotube and fullerene, in 2004, two scientists, Andre Geim and Konstantin Novoselov of Manchester University, UK, have obtained a slice composed of a layer of carbon atoms in laboratory, which is graphene. Due to the groundbreaking experiment of two-dimensional material of graphene, Andre Geim and Konstantin Novoselov won the 2010 Nobel Prize in Physics.
So far, graphene is a material that having the best electrical conductivity, in which the electron velocity reaches 1/300 of velocity of light, far exceeding the electron velocity in general conductor. Since graphene has properties of ultra-thin and super strength properties, it can be widely used in various fields, such as ultra-light body armor, ultra-thin and ultra-light aircraft materials, and the like. According to its excellent conductivity, it also has great application potential in the field of microelectronics. In the future, graphene is expected to replace traditional silicon materials, to manufacture ultra-miniature transistors, for producing future supercomputers, while higher electron mobility of carbon enables the future computers achieve higher speeds. Besides, graphene material is an excellent modifier, in the field of new energy, e.g., super-capacitors and lithium ion batteries, due to its high conductivity, high specific surface area, transparency and other characteristics; it is suitable for use as an electrode material. Graphene also can be used as ultra-thin, super-strong, transparent, flexible conductor, to substitute brittle, expensive, indium tin oxide, and is widely used in a touch screen, LCD, and a solar cell and the like. In a word, graphene has a wide application range, and its emergence is expected to lead a new round of revolution in the field of modern electronic technology.
However, the realization of the physical properties and potential applications of graphene cannot be separated from the preparation of high-quality, low-cost, large-scale graphene. Currently, the main methods for preparing graphene are: a micro-mechanical stripping method, a chemical vapor deposition method, a SiC surface graphitization method, an organic molecule dispersion method, an ion intercalation method, a solvothermal method, an oxidation-reduction method, a C-doped precipitation method, etc. In the micro-mechanical stripping method, ion beam is adopted to etch material surface, and then the material surface is stripped by mechanical force to prepare graphene. However, because of the complexity of process, the prepared graphene has low yield, which is unable to meet the demand of industrialization, to a certain extent, limits the large-scale production. Chemical vapor deposition method is a film growth method that forms a graphene thin film on a substrate surface by using a chemical reaction, and it has been reported that CO is changed into gaseous carbon atoms via its reduction by CH4, and the product deposits on a substrate surface, to form two-dimensional graphene films. Since CH4 has high decomposition temperature, this method is only suitable for a small number of substrate materials resistant to high temperature. SiC surface graphitization method is that, under ultrahigh vacuum, 4H—SiC or 6H—SiC was heated above 1300° C., then Si atoms on the SiC crystal surface are evaporated and a reconstruction of carbon atoms occur, so that two-dimensional graphene films are formed on the surface of Si single crystal. The thickness of the graphene films prepared by such method is only 1 to 2 carbon atoms layer, with high carrier mobility. But the graphene prepared by using such method fails to observe quantum Hall effect, and the electronic properties of graphene surface greatly affected by the SiC substrate, and further research is still in progress. In the organic molecule dispersion method, graphite is ultrasonic dispersion in organic solvent to obtain the graphene, and the graphene prepared by such method has fewer defects, but the concentration is not high. In the ion intercalation method, firstly graphite intercalation compounds are prepared, and then graphene is dispersed and prepared in an organic solvent; while the graphene prepared by such method has lower dispersion. In the solvothermal method, reactant is added into a solvent, and by taking the property that above the critical temperature and critical pressure, the solvent enables to dissolve the vast majority of substances, the reaction that cannot occur under normal conditions enables to occur at lower temperatures (at a high pressure) or to be accelerated. This method features short development time; while many theoretical and technical issues at this stage still cannot break through yet, and should be further explored. In the oxidation-reduction method, graphite is oxidized to obtain oxidized graphene dispersed in a solution, which is further reduced by a reducing agent to prepare graphene; it has low cost, high yield, but the graphite completely oxidized by a strong oxidant is hard to be completely restored, resulting in loss of some physical and chemical properties, especially the loss of conductivity. In the C-doped precipitated method, MBE is used to grow C-doped GaAs material, which is further decomposed by raising the temperature, therein the C atom is precipitated to form graphene; this method has low controllability, and the generated graphene has a relatively low quality, and is still on the groping stage. It is requisite to improve the existing level of preparation method, and currently, the preparation of graphene is still a technical problem in this field.
The convenient method of this invention, by taking CBr4 as a source material, for directly preparing graphene, may prepare a continuous, large-area graphene film material on many substrates, and the existing semiconductor process techniques may perform tailoring modification on the graphene film material, such that the graphene materials prepared by such method has great application potential in microelectronics and optoelectronics fields.